Endoscopic needle knives may be used to perform various electrosurgical medical procedures, such as endoscopic submucosal dissection (ESD) or endoscopic retrograde cholangiopancreatography (ERCP) on tissue within a patient. An endoscopic needle knife may be used as an alternative to a sphincterotome, particularly where the sphincterotome is unable to cannulate the papilla. The endoscopic needle knife may include a cutting wire disposed within a catheter. The cutting wire may be moved so that a distal end of the cutting wire distally extends past the catheter to a desired location. The distal end of the cutting wire may contact the tissue, and an electrical current may be sent along the cutting wire to perform the electrical procedure.
During operation of the endoscopic needle knife, various forces may be exerted on the endoscopic needle knife that may cause longitudinal movement of the cutting wire relative to the tubular member. For example, forces due to hysteresis as the needle knife moves between tortuous to straight positions within a working channel of the endoscope may cause the cutting wire to move. Additionally, the cutting wire may move when the distal end comes into contact with the tissue at the treatment site. Consequently, the distal end of the cutting wire may move or be displaced from its desired location, and the amount of cutting wire exposed at the distal end may uncontrollably vary.